Early Pregnancy Scans 3–6 Weeks: A Complete Guide for 2026

You’ve just received those two pink lines. Or the words “Pregnant” leaping out at you from the test. Your first instinct is probably to ring up and book a scan ASAP so you can see what’s happening in there. That’s totally understandable. But did you know that the timing of an early pregnancy scan matters more than you realise and having one too early can lead to unnecessary stress?

We explain everything you need to know about early pregnancy scans in London, from 3-6 weeks, what you can expect to see at each stage and why timing is important. We also cover when you can access one on the NHS too.

What Are Early Pregnancy Scans and Why Do People Get Them?

An early pregnancy scan is one performed before your standard NHS 12 week dating scan. As scans aren’t offered on the NHS until about 10–14 weeks for most women in the UK, those that require or want reassurance (or have medical indication to investigate) book privately.

Scans this early can be requested for many reasons: previous miscarriage, bleeding or cramping, uncertain dates, conceived via IVF, previous ectopic pregnancy or your just worried that everything’s ok. There are many reasons to want to take a look earlier.

At myGynaePlus we offer early pregnancy viability scans from as early as 6 weeks by senior specialists using the latest imaging technology. We will provide you with results on the day and ensure appropriate follow up care where necessary.

Week-by-Week: What Can You Actually See?

This is where a lot of confusion happens. What the scanner can show depends entirely on how far along the pregnancy is  and even a difference of a few days makes a real difference to what’s visible.

3 Weeks Pregnant: Too Early to Scan

The fertilised egg is only just implanting into the wall of the uterus at 3 weeks. There won't be anything to see on a scan, not even a gestational sac. Your pregnancy is far too small to be detected by ultrasound scan in London or any other scan.

What clinicians can see at this stage is a blood test to measure hCG levels. This is the hormone produced by your placenta when pregnant. hCG doubles roughly every 48 hours in early pregnancy, so repeated blood tests can reassure you when a scan cannot. If you book a scan at 3 weeks you will not get any meaningful information from it.

4 to 4.5 Weeks: The Gestational Sac Appears

The first thing that will show up on your scan in early pregnancy is called the gestational sac. From StatPearls on NCBI we learn that the gestational sac can be detected by transvaginal ultrasound as early as 4.5 – 5 weeks, with its diameter measuring about 2–3 mm at first. It looks like a small round fluid filled blob within the uterus.

Finding that gestational sac in the proper place neatly inside the uterus is very reassuring, as that means it’s not an ectopic pregnancy. However, just because you see a sac doesn’t mean you are definitely pregnant. There are other structures that must develop before we can make that determination.

5 to 5.5 Weeks: The Yolk Sac

Around 5-5.5 weeks there should be a yolk sac visible within the gestational sac. It appears on screen as a small white ring. The yolk sac provides nourishment to the embryo prior to the placenta developing sufficiently. Its presence indicates development is progressing as it should.

It's at this stage that an internal/transvaginal scan (a small probe inserted internally) provides a much clearer image than a scan via the abdominal wall. Buckinghamshire Healthcare NHS Trust states that transvaginal scanning is the optimal way to examine an early pregnancy of less than 10 weeks as it provides clearer detail.

A yolk sac larger than 7 mm can indicate a problem but results are always read by a trained clinician who will take all results into consideration.

6 Weeks: The Fetal Pole and Heartbeat

Six weeks is the point that most private clinics recommend for a first viability scan. Here’s why.

By 6 weeks, a small structure called the fetal pole appears adjacent to the yolk sac. As described in peer-reviewed literature from the National Library of Medicine, the fetal pole is a small, echogenic linear or oval structure measuring about 1–2 mm in length  roughly the size of a grain of rice. This is the earliest visible form of the embryo.

Crucially, cardiac activity can often be detected at this stage. The Society and College of Radiographers advises that waiting until around 6–7 weeks gives a clearer view of the heartbeat. At 6 weeks and beyond, the embryo’s heart rate can typically be seen flickering on the screen. Seeing this is a significant milestone  once a heartbeat is confirmed at this stage, the risk of miscarriage drops considerably.

What to expect on an early pregnancy scan  week by week:

• 3 weeks: Nothing visible on scan; hCG blood test is the only option

• 4–4.5 weeks: Gestational sac visible on transvaginal scan (2–3 mm)

• 5–5.5 weeks: Yolk sac visible inside the gestational sac

• 6 weeks: Fetal pole (1–2 mm) visible; cardiac activity often detectable

• 6.5–7 weeks: Heartbeat clearly visible; crown-rump length measurement possible

Transvaginal vs. Abdominal Scans: Which One Will You Have?

Many women anticipate that their pregnancy scan will involve abdominal scanning with the probe going on your belly, as pictured in the movies. This isn’t always the most informative method during early pregnancy.

Transvaginal ultrasound involves inserting a thin probe into your vagina. This provides a clearer picture within the first 10 weeks as the probe is nearer to the uterus. It’s way less awkward than it sounds. Your sonographer will cover the probe with a sterile covering and apply a lubricating gel. They will also ensure that the procedure is conducted at your pace. Rest assured that both techniques are safe and carry no risk of miscarriage.

Tommy’s (the UK pregnancy charity) states that transvaginal scanning will often be offered to patients during the first 6–7 weeks of pregnancy or anytime the abdominal scan isn’t providing enough information. Beyond 9-10 weeks, your midwife will likely only need to do an abdominal scan.

Read More: Early Signs of a Urine Infection During Pregnancy

Why the Timing of Your Early Scan Matters

Scanning too early is one of the top reasons women cause unnecessary anxiety during early scans. You may schedule a scan at 5 weeks only to see a gestational sac. You may immediately think something is wrong but really your pregnancy may just be too early. Certain structures have not had enough time to develop.

When you only see a gestational sac, UT Southwestern Medical Center states “the usual advice is to wait two weeks and reschedule the ultrasound.” If you see a yolk sac but no fetal pole, wait at least 11 days to repeat the ultrasound. Going back too soon can lead to more ambiguous results and more stress not less.

Scanning at 3 weeks or even very early 4 weeks is also not recommended for this same reason. A negative or unclear result doesn’t mean something is wrong, it means your pregnancy is too early to tell by ultrasound.

The sweet spot for a private early viability scan is between 6 and 8 weeks. By this point, you can usually confirm:

• The pregnancy is inside the uterus (not ectopic)

• Whether there is one sac or more (identifying twins)

• That a heartbeat is present

• An estimated due date based on crown-rump length measurement

  
  

When the NHS Offers Early Scans

The NHS does offer early scans, but usually only for specific medical reasons. If you have experienced unexplained bleeding, significant pelvic pain, or a previous ectopic pregnancy, your GP or midwife can refer you to an Early Pregnancy Assessment Unit (EPAU). Most NHS early scans happen between 6 and 8 weeks.

If you’ve had a previous miscarriage, you may also be offered an early reassurance scan. Tommy explains that this is to help assess the viability of the pregnancy and provide some peace of mind, rather than as standard routine care.

If you don’t meet the medical referral criteria but want a scan for reassurance, going privately is the usual route.

What Happens If Results Are Inconclusive?

Not every early scan will produce a definitive result and that’s not necessarily bad news. If a scan reveals a gestational sac but no yolk sac or fetal pole just yet, it could just be that your pregnancy is a little earlier than you thought.

At myGynaePlus we’ll review your results with you on the day and organise suitable follow up. This could be a repeat scan 10–14 days later or a blood test to monitor your hCG levels. No reputable clinic will make a diagnosis that a pregnancy isn’t viable based on one inconclusive early scan - current guidelines are clear that a repeat scan should be performed before anyone reaches that conclusion.

Should you have bleeding or pain, your clinical team will take appropriate action and you will be referred for further investigations or NHS care where necessary.

Frequently Asked Questions

Can I get an early pregnancy scan at 4 weeks?

Technically yes, but you’re unlikely to see much beyond a very early gestational sac  and only with a transvaginal scan. At 4 weeks, there’s no yolk sac or fetal pole yet, so the scan won’t be able to confirm viability. Most clinicians recommend waiting until at least 6 weeks for a meaningful early viability scan.

What does it mean if no heartbeat is seen at 6 weeks?

It doesn’t automatically mean something is wrong. Some pregnancies develop slightly more slowly, or your dates may be off by a few days. Clinicians generally recommend a repeat scan 10–14 days later before drawing any conclusions. An absent heartbeat at exactly 6 weeks is not diagnostic of pregnancy loss on its own.

Is a transvaginal scan safe in early pregnancy?

Yes. Transvaginal ultrasound is safe throughout pregnancy and does not increase the risk of miscarriage. It uses sound waves, not radiation, and is the preferred method for early pregnancy imaging because it gives a clearer picture than an abdominal scan in the first trimester.

Will the NHS give me an early scan before 12 weeks?

The NHS offers early scans in specific circumstances usually if you have symptoms like unexplained bleeding, significant pelvic pain, or a history of ectopic pregnancy. If you want a scan for reassurance without a medical indication, you’ll generally need to book privately. Your GP or midwife can advise on whether a referral is appropriate.

How accurate is early pregnancy dating at 6 weeks?

At 6 weeks, once a fetal pole is visible, the crown-rump length (CRL) measurement gives a good estimate of gestational age. Dating from CRL is considered more accurate than using your last menstrual period, especially if your cycles are irregular. If the scan date differs considerably from your expected dates, your due date may be adjusted accordingly.